Hindawi Contrast Media & Molecular Imaging Volume 2017, Article ID 7350429, 8 pages https://doi.org/10.1155/2017/7350429
Research Article An Individually Optimized Protocol of Contrast Medium Injection in Enhanced CT Scan for Liver Imaging Shi-Ting Feng,1 Hongzhang Zhu,1 Zhenpeng Peng,1 Li Huang,1 Zhi Dong,1 Ling Xu,2 Kun Huang,1 Xufeng Yang,1 Zhi Lin,1 and Zi-Ping Li1 1
Department of Radiology, The First Affiliated Hospital, Sun Yat-sen University, 58th, The Second Zhongshan Road, Guangzhou, Guangdong 510080, China 2 Faculty of Medicine and Dentistry, University of Western Australia, Perth, WA, Australia Correspondence should be addressed to Xufeng Yang;
[email protected], Zhi Lin;
[email protected], and Zi-Ping Li;
[email protected] Received 28 December 2016; Revised 26 February 2017; Accepted 29 May 2017; Published 10 July 2017 Academic Editor: Silun Wang Copyright © 2017 Shi-Ting Feng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objective. To investigate the effectiveness of a new individualized contrast medium injection protocol for enhanced liver CT scan. Methods. 324 patients who underwent plain and dual phase enhanced liver CT were randomly assigned to 2 groups: G1 (𝑛 = 224, individualized contrast medium injection protocol); G2 (𝑛 = 100, standard contrast medium injection with a dose of 1.5 ml/kg). CT values and ΔHU (CT values difference between plain and enhanced CT) of liver parenchyma and tumor-liver contrast (TLC) during hepatic arterial phase (HAP) and portal venous phase (PVP) and contrast medium dose were measured. The tumor conspicuity of hepatocellular carcinoma (HCC) between two groups was independently evaluated by two radiologists. Results. The mean contrast medium dose of G1 was statistically lower than that of G2. There were no significantly statistical differences in CT values and ΔHU of liver parenchyma during HAP, TLC values during HAP, and PVP between two groups. The CT values and ΔHU of liver parenchyma during PVP of G2 were significantly higher than those of G1. Two independent radiologists were both in substantial conformity in grading tumor conspicuity. Conclusion. Using the individually optimized injection protocol might reduce contrast medium dose without impacting on the imaging quality in enhanced liver CT.
1. Introduction The use of contrast enhanced computed tomography (CT) with iodinated contrast medium (ICM) has significantly improved the accuracy of imaging diagnosis. The rapid development of CT technologies has led to an increase in world-wide usage of ICM. This also results in an increase in its associated adverse reactions, where contrast-induced nephropathy (CIN) is one of the most concerning adverse effects by far. As early as 2001, M. M. Waybill and P. N. Waybill [1] reported that CIN had become the third leading cause of all hospital-acquired renal insufficiency. Since kidney is the primary organ where ICM is metabolized, higher dose of ICM may cause greater damage to the kidney, hence resulting in higher incidence of CIN [2]. Davidson et al. [3] reported that incidence of CIN proportionally correlates with the contrast medium dose used especially amongst high-risk
populations with preexisting renal insufficiency or diabetic neuropathy. Therefore, on the premise of ensuring the quality and display capability of CT images, reasonable reduction in contrast medium dose may effectively prevent and reduce the incidence of adverse effects associated with enhanced CT scans. Various methods had been previously proposed to reduce the contrast medium dose, including individualized weight-based protocols [4–8], adjustment on the injection time or flow rate of contrast administration [9–11], and the use of additional saline flush [12–14]. Out of the various options, previous reports had demonstrated that personalized weight-based contrast medium injection protocol is an ideal method to reasonably reduce the injection dose of contrast medium [8]. Personalized patient protocol technology abdomen module is a new intelligent platform, which enables the generation
2 of individualized contrast medium injection protocol based on patient characteristics (such as weight), contrast medium properties (such as iodine content), and other procedure parameters (such as scan timing). P3T (Bayer Healthcare, Berlin, Germany) is designed as an individualized contrast medium injection protocol software adapting the iodine delivery rate and total iodine load based upon a nonlinear relationship between patient weight and scan duration in order to achieve diagnostic attenuation. By using patient weight, scan duration, contrast medium concentration, and timing attributes of a test bolus scan, P3T facilitates customizing injection protocol for each patient and procedure. Previous studies have shown that this customized injection software could lead to diagnostic and comparable attenuation values in the coronary CTA for every individual patient and a more efficient use of contrast medium dose [15, 16]. However, the application of this individually optimized protocol of contrast medium injection in liver imaging has not been evaluated previously. In this study, we aimed to evaluate whether this new contrast medium injection protocol can reduce the contrast medium dose used in enhanced CT scan for liver imaging without limiting the quality of the images.
2. Materials and Methods 2.1. Patients. This prospective study was conducted in accordance with ethical guidelines for human research and was compliant with the Health Insurance Portability and Accountability Act (HIPAA). The study has been approved by the Institutional Review Board (IRB) or ethical committee. Written informed consent was obtained from all patients in the study. All patients who underwent liver CT scan in our hospital between January 2013 and December 2015 were included in this study. Exclusion criteria were large liver lesions (diameter > 5 cm), diffuse liver diseases such as cirrhosis (suggestive CT findings include abnormal size and shape of liver and spleen, inhomogeneous liver appearance with regenerating nodules and/or signs of portal vein hypertension [17]) and multiple metastases, postliver resection, severe fatty liver (liver density lower than spleen in unenhanced CT), cardiac insufficiency (Grades II, III, and IV, NYHA), liver insufficiency (liver function Child-Pugh B and C), renal failure (1–5 stages, chronic kidney disease (CKD)), and known allergies to contrast medium. In the end, a total of 324 cases were included. All patients were randomly assigned to either Group 1 (G1) or Group 2 (G2). 224 patients were randomized into G1, with mean age of 47.7 ± 11.7 years and mean weight of 59.8 ± 10.9 kg; 100 patients were randomized into G2, with mean age of 53.9 ± 12.0 years and mean weight of 61.8 ± 10.4 kg. There were no statistical differences in patient age and weight between G1 and G2 (𝑃 > 0.05). A total of 38 patients with histopathologically proven hepatocellular carcinoma (HCC) were included in the study. 23 patients (18 male and 5 female; mean age of 63.4 years) were randomized to G1 and 15 patients (13 male and 2 female; mean age of 58.3 years) to G2.
Contrast Media & Molecular Imaging 2.2. CT Scan Protocols. All patients were scanned using a 64-detector row CT machine (Aquilion 64, Toshiba Medical System, Tokyo, Japan) using same scanning parameters as follows: tube voltage, 120 kV; tube current, 250 mAs; rotation time, 0.358 s; field of view, 400 mm; reconstruction interval, 1 mm; slice thickness, 0.8 mm. All patients underwent both unenhanced and enhanced CT scans during hepatic arterial phase (HAP) and portal venous phase (PVP). According to Mihl et al. and Tu et al. [16, 17], all the enhanced CT scans during HAP and PVP in the present study started at 35 s and 65 s, respectively, after the contrast injection, from the level of diaphragm to inferior hepatic edge. Both groups received the same contrast medium with an iopromide concentration of 300 mgI/mL (Ultravist, Bayer, Germany) injected at a flow rate of 3 mL/s. G1 adopted an individually optimized protocol (P3T abdomen module, Medrad Inc.) of the platform, which automatically calculates the contrast medium dose based on the weight of each patient by using weight factor dosing method calculated from the following formula: Contrast volume (ml) =
Weight Factor (gI/kg) ∗ patient Weight (kg) (1) . Contrast Concentration (mg/ml) ∗ 1000
The weight factor is expressed in grams of iodine per kilogram of patient weight and specified as 0.4 gI/kg. Contrast medium concentration is 300 mgI/kg. The formula uses both patient weight and contrast concentration for determining an individualized contrast dose. This module automates the calculation of individualized contrast injection protocols. By providing the patients’ weight, iodine concentration, and either the flow rate or duration for the contrast injection protocol, P3T Abdomen will generate a protocol specifically tailor to the patient by delivering customized contrast through weight-based calculation. According to Megibow et al. [7], acceptable image quality can be obtained for most patients by using low osmolar contrast medium with an iodine concentration of 300 mg/ml given at a dose of 1.5 ml/kg based on body weight. Therefore, in this study, G2 candidates received a standard contrast medium injection protocol with a contrast medium to weight dose of 1.5 ml/kg. 2.3. Quantitative Image Analysis. Quantitative analysis was later performed on the workstation (HP Workstation XW8200, Vitrea 2, Version 3.7). CT values of unenhanced liver parenchyma, CT values of liver parenchyma during HAP and PVP, and CT values of the portal vein during PVP were measured via regions of interest (ROIs) on the axial images. The CT values of liver parenchyma were measured in three liver sections (right anterior, right posterior, and left lateral segments) and the mean values were calculated. The ROI was circular with a fixed area of 0.5 cm2 . Caution was taken during measurement to avoid the interference of vessels, edges, bile duct, intestine, and so on ROI was placed at the portal vein trunk, and the edges of ROI should be as close as possible to the edge of the vessel wall on both sides of the portal veins. The liver parenchyma enhancement ΔHU
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Table 1: Results of CT values of liver parenchyma and liver parenchyma ΔHU during HAP and PVP, CT values of portal vein during PVP, and contrast medium dose in G1 and G2.
G1 G2 𝑃
CT values of liver parenchyma during HAP (HU)
CT values of liver parenchyma during PVP (HU)
CT values of portal vein during PVP (HU)
Liver parenchyma ΔHU during HAP (HU)
Liver parenchyma ΔHU during PVP (HU)
Contrast medium dose (ml)
77.3 ± 11.9 76.0 ± 11.5 0.367
102.6 ± 9.5 106.4 ± 11.3 0.001
147.0 ± 15.4 159.7 ± 18.4
